This invention relates to a process for converting brines into useful products, and more particularly to converting saline waters such as oil and gas field brine wastes, seawater or effluent from a seawater desalination plant, or other inland saline waters into animal feed supplements, fertilizer, salt, purified brine and purfied water.
Oil and gas field operations generate waste products in the production and handling of crude oil and natural gas. These waste products include drilling mud pit waters and oil and gas field brines. The quantities of brines produced in oil and gas fields can be substantial, with brine fractions accounting for from 4 to 96 percent of the total liquid volume produced. Brines from other inland or seawater sources also present disposal problems.
Various method of disposal of these brines have been attempted including solar evaporation, thermal evaporation, controlled release of brines into surface water, and injection of brines into subterranean formations. However, in areas of high annual rainfall and/or high relative humidity, such as much of the midwestern and eastern portions of the United States, solar evaporation becomes impractical. Moreover, with increasing state and federal regulatory pressures, diversion of large volumes of brine into surface waters is not an environmentally acceptable solution.
While evaporation as a means of recovering fresh water from these saline sources has been attempted, the presence in such brines of a large proportion of divalent metal chlorides such as calcium and magnesium chloride have greatly complicated recovery efforts. These metal chlorides are highly corrosive to process equipment surfaces and deposit hard to remove mineral scales. This scale deposition becomes an even greater problem when the brines are heated.
Presently, brine treatment using dissolved air flotation methods to remove suspended oil, followed by deep well injection of the brine is regarded by the United States Environmental Protection Agency as the best practicable technology for disposal. However, deep well injectin is expensive, difficult to design to a given level of capacity, and requires careful conditioning of the brine prior to injection. Also, deep well injection of brines may present a contamination hazard to fresh water aquifers. Economies of scale favor deep well injection systems having capacities of millions of gallons of brines per month. However, in oil and gas fields in the midwestern and eastern United States where less brine wastes are produced than in western oil fields, and where the oil and gas fields themselves are smaller, deep well injection may not, in many instances, be an economically feasible disposal alternative.
Some attempts have been made in the past to separate useful byproducts from brines or other industrial waste waters. For example, Miller, U.S. Pat. No. 3,374,081, teaches a method of precipitating minerals from saline waters using lignin compounds, proteinaceous compounds, and tannins. The saline waters are initially concentrated by evaporation and the resultant salt precipitate removed. Then an organic precipitating agent such as a lignin or tannin is added to form an organic fertilizer containing other inorganic minerals.
Baldassari, U.S. Pat. No. 4,069,033, teaches the extraction of fertilizer salts and organic substances from a variety of industrial waste waters including sugar mill, distillery, and fermentation wastes. Baldassari teaches the use of strong acids or bases to form precipitates from such waste waters which precipitates are taught to be useful as fertilizers. However, neither of these particular procedures is believed to have gained widespread use.
Accordingly, the need exists for a cost effective and environmentally acceptable method for the disposal of oil and gas field waste brines and other saline water sources.